Drive units for an automatic steering of vehicles used in landscaping, farming and soil care are known from prior art. Such automatic steering systems are needed to economise fuel and/or agricultural material, to unburden manpower and to improve field coverage during a processing job. For example, overlaps may be avoided, when ploughing soil, mowing grass, spreading fertilizer or harvesting crops. Furthermore, a specifically directed route along a predetermined path may be required, for which positional systems, such as GNSS or RADAR based systems are typically used along with the steering control.
These steering control systems typically comprise a mechanical steering assembly conventionally consisting of a steering wheel, a steering column encompassing a steering rod, a rack and a pinion, tie rods and kingpins. They further comprise a drive unit for a controlled driving of the steering assembly, e.g. by means of the steering wheel itself, or by means of the steering rod mounted in the steering column.
Known vehicle steering systems are built deep into the vehicle interior and are therefore quasi permanently fixed and immovable. A control unit manages a motor adjusting the position of a steering wheel or steering rod, whereby the steering wheel usually is still usable by a driver, and the control unit either takes over when the driver is not steering or intervenes when the command of the driver needs to be corrected. One disadvantage of such a system is that it only comes with the vehicle and is therefore not withdrawable and mountable into other vehicles which are not yet equipped with such automatic steering system.
Other vehicle guidance systems, such as disclosed in the patent publication U.S. Pat. No. 8,892,308, are therefore portable, and mountable on a steering column, where they provide a motor for directly driving a steering rod. With this, a driver may take his steering assembly from vehicle to vehicle, or “modernise” an existing vehicle by implanting such guidance system into it.
However, with drive units from prior art it is not possible or not satisfyingly possible to further configure the drive characteristics and therewith adapt to specific circumstances or vehicle properties. Especially when the vehicle guidance system must be modular and mountable into different vehicles, one motor configuration must fit all settings. For example, when unfavourable circumstances such as muddy and sticky underground or special vehicle properties, such as dimensions of wheels or heavy duty are given, the engine map of a motor of a driven steering system may not be suitable to satisfy the requirements of the steering.